Couplings are known in the art for interconnecting a rotatable driving shaft and a rotatable driven shaft. The driving shaft is typically driven by a prime mover or motor, and the driven shaft is connected to and drives a rotatable machine or load such as a pump or compressor, for example. Rotation of the driving shaft causes a corresponding rotation of the driven shaft via the coupling. The coupling allows for slight misalignment of the driving and driven shafts such as radial offsets, angular misalignments of the axes of the shafts, or both.
One such coupling is the “insert (3-jaw) type”, such as that manufactured by Boston Gear, in which each coupling half (coupling body) has three axially extending jaws spaced about the circumference of a respective plate-like end flange. A spider with six radially outwardly extending legs is disposed between the coupling halves, and the couplings are axially positioned so that the each jaw of one coupling half is disposed between two jaws of the other coupling half, and separated from each of the two jaws of the other coupling half by a respective one of the spider legs. The spider is typically made of a material which is relatively softer than that of which the coupling halves are made. It is known to make the spiders of oil-impregnated bronze, synthetic rubber, polyurethane, urethane, and co-polymer thermoplastic elastomers. When one of the coupling halves is rotated, torque is transmitted from each of the jaws of the driven coupling half, through an adjacent one of the spider legs to the adjacent jaw of the other coupling half, thereby causing rotation of the other coupling half. Because the jaws and spider surfaces are flat, axially oriented surfaces, this arrangement allows for a certain amount of rotational play and backlash.
Other couplings currently known in the art often permit this undesirable rotational play or backlash between the driving shaft and the driven shaft. The rotational play can result in undesirable wear and damage to the shafts and the couplings. Additionally, undesirable noise and vibration to the load or prime mover can result.
Manufacturers have attempted to control rotational play using couplings of two types. One type includes elastomeric coupling elements which deform to form a close fit to the driving shaft and the driven shaft (similar to the “insert (3-jaw) type”). The inclusion of the elastomeric coupling elements may prevent the coupling from being used under certain environmental conditions. Another type requires some form of fastening to the driving and driven members to eliminate relative motion, thereby causing an undesirable increase in production costs.
It would be desirable to produce a coupling which militates against rotational play between the driving shaft and the driven shaft.